CMX654 データシートの表示（PDF） - CML Microcircuits

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CMX654

V23 Transmit Modulator

CML Microcircuits 

V.23 Transmit Modulator

CMX654

1.5.2 Mode Control Logic

The CMX654's operating mode is determined by the logic levels applied to the M0 and M1 input pins:

M1

M0

0

1

1

0

1

1

Tx Mode

1200bits/sec

off

'Zero-Power'

Data Retime[1]

Tx

-

-

[1] If enabled.

In the 'Zero-Power' mode, power is removed from all internal circuitry. When leaving 'Zero-Power' mode there

must be a delay of 20ms before any Tx data is passed to the device to allow the bias level, filters and oscillator

to stabilise. On applying power to the device the mode must be set to 'ZP', i.e. M0=1, M1=1, until VDD has

stabilised.

1.5.3 FSK Modulator and Transmit Filter

These blocks produce a tone according to the TXD, M0 and M1 inputs as shown in the table below, assuming

data retiming is not being used:

M1

M0

TXD = '0'

TXD = '1'

1

1

-

1

0

0Hz[1]

0

1

2100Hz

1300Hz

Note: [1]

TXOP held at approx VDD/2.

When modulated at the appropriate baud rates, the Transmit Filter and associated external components (see

Section 1.6.1) limit the FSK out of band energy sent to the line in accordance with Figure 3 assuming that the

signal on the line is at -6dBm or less.

© 1998 Consumer Microcircuits Limited

Figure 3 Tx limits

6

D/654/3

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